Method of and mechanism for drying materials



Sept. 24, 1929- w. .1. HARSHAW El AL METHOD OF AND MECHANISM FOR DRYINGMATERIALS Filed Feb. 9, 192 1 IyVENTORS BY filer/c6 J. Far/re.

ATTORNEYS Patented Sept. 24, 1929 UNITED STATES PATENT OFFICE- WILLIAMJ. HARSHAW, E SHAKER HEIGHTS VILLAGE, AND CHARLES s; PARKE, 0E oEvELnNn, oHIo, AssIeNbRs, BY MESNE ASSIGNMENTS, TO THE HARSHAW CHEMICALCOMPANY, OF CLEVELAND,

OHIO, A CORPORATION OF OHIO METHOD OI AND MECHANISM FOR DRYING MATERIALSApplication filed February 9, 1924. Serial No. 691,607.

Our present improvements are applicable to any finely divided wetsubstance, such for example as press cake of any material, e. g., achemical precipitate that is preliminarily separated from the liquid inwhich such precipitate is formed by means of a filter press.

Our improved process and mechanism are equally adapted for drying slimesfrom mining and metallurgical operations and a va- .0 riety of otheruses might be suggested were it deemed necessary. The field of use,however, will sufliciently appear from the following description. Theobject of the invention is to provide a self-contained process and v5apparatus wherein'materials of the sort described may be simultaneouslydried and pulverized, the material being in effect automatically removedas fast as it is reduced to the desired dry state and pulverulent condi-50 tion..

To the accomplishment of the foregoing and related ends, the inventionaccordingly consists of the steps and means hereinafter fully describedand particularly pointed out in the claims, the annexed drawing and thefollowing description settingforth but one of the various ways in whichthe principle of the invention may be used.

In said annexed drawing The single figure there appearing is a more orless diagrammatic representation of a mechanism or apparatus adapted forcarrying out our. improved process.

Referring to the illustrative apparatus shown in the drawing, thematerial tobe treated, i. e.,'dried, is supplied by'means of a hopper 1equipped with a feed screw 2 to one endIof a horizontally disposedrotary drum 3, preferably of the general form shown.

In otherwords, such drum comprises a central cylindrical portion withend portions having the shape of conical frusta. This drum is rotatablysupported in any suitable manner, as for example upon rollers 4, andpower means, not shown, are provided forrotating same at any desiredrate of speed. Within the drum may be placed a number of balls 5 ofhard, resistant material, for .example iron or steel,which are adaptedto come in contact with any material within the dru-m as the latte-r isrotated and tend to pulverize and grind such materiahas will be readilyunderstood. When the filter press cake, or other material being handled,is a mass of finely divided particles loosely cemented together, ormere-1y agglomerated by the moisture present, the agitation resultingfrom the rotation of the drum will frequently suffice to pulverize suchmaterial without the use of any other grinding means such as the balls5. It will accordingly be understood'that the term pulverizing ashereinafter employed does not imply the use of any special grindingagency where the material is capable of being reduced to a pulverulentform by simple dry ing and agita ion.

Connected with the same end of the drum 3 into which the material isintroduced from hopper 1 is a pipe or duct 6 and interposed in such ductis an enlarged heating chamber 7 equipped with a steam coil 8, wherebyair circulating through such duct may be raised to any desiredtemperature. It will be understood, of course, that any suitable meansfor thus heating the air passing through such duct and into the drum,may be employed in place of the specific heating chamber just described.A second pipe or duct 9 leads from the opposite, i. e. discharge, end ofdrum 3 to a settling chamber or dust separator 10'which' is in turnconnected by means of a duct 11 with the intake side of a fan 12. Thisfan is connected to discharge into the outer reach of duct 6, so.thatthe several ducts 6, 9 and 11, with interposed heating chamber 7,settling chamber 10 and fan 12, areadapted to provide a closedcirculatorysystem, whereby heated air may be passed through drum 3 12 isconnected with the latter, to the lower ends of one or more dustcollecting chambers 9 14 of familiar-construction, the upper ends ofthese chambers being connected by means of a duct 15 with a suction fan16. Suitable ivalves 17, or equivalent means, are provided fordischarging any material that may accumulate in the lower portions ofsuch dust collectors 14.

The duct 6 is connected or, as is shown, is continuous with an extension18 at a point in advance of heating chamber 7, having regard tothe,direction in which the air'is circulated through said duct. Thisextension of duct 6 in effect forms part of a duplicate circulatory syscm similar to the one just described, in that in a duct 19, that leadsfrom such extension 18, a heating chamber 20 is interposed, such duct 19connects with a drum 20,similar to drum 3, the discharge end of thelatter is connected by means of a duct 21 with a dust separator22,.similar to separator 10, and a duct 23 leads from the latter to afan 24, which discharges back into extension 18 through a duct 25. Thematerial that settles out in'collector 10 is transferred by means of aconveyor 26 to ahopper 27, similar to hopper l, and like it providedwith a feed screw 28, whereby such material is fed into the intake endof drum 20. Collector 22 is provided ,fivith a discharge valve 29, orequivalent ;-'means, whereby the material accumulating therein ma fromtime to time be removed. It will furt er be noted that duct extension 18is open at a point 30 in advance of heating chamber 20, such openingbeing controlled by a valve 31. A valve 32, is likewise provided in saidduct 18 between its connection with heating chamber 20 and the, pointwhere the return duct 25 connects with said duct 18; while a third valve33 is located in duct 6 in advance of heating chamber 7 and the pointwhere the extension 18 leads ofi from said duct.

. The operation of the apparatus may now be inclusively described.Assumin valve 31 to be closed and valves 32 and 33 to e open, andmaterial in raw state, so far as the apparatus in hand is concerned, forexample filter pressed cake with a 50 per cent moisture content, to befed from hopper 1 into the first rotary drum 3, a circulation of airwill be maintained through said,drum by proper operation of fan 12 andsuch air heated to a temperature 'sufiiciently high to remove the waterpresent in the material to the'desired degree. This removal isfacilitated by the agitation or stirring of the material due to rotationof the drum and at the same time the effect ofthe balls 5 will be tobreak up the material and reduce it to a pulverulent condition. As fastas this occurs and the particles become dry enough to be carried off bythe current of air, they will be conveyed b the latter to the dustcollector 10 and there a owed to settle out.

Fromcollector 10 the material is conveyed tohopper 27 and thenceintroduced into-the second rotary, drum 20 where the same operation .isrepeated, the air that; ispirculated -t.hm gh;such: dmin y? means or,fan arteing-haatedzta a temperature sufliciently high moisture thematecarryalongthe-dried particlesefithe material, 1:

to remove the residual rial or reduce such moisture to a desiredminimum.

v In other words, with the valves in the positions referred to, eachcirculatory system would operate as-an independent unit, but it isnecessary of course that air should be discharged from both systems toprevent it from becoming saturated with moisture and accordingly thevalve 31 will be partially open so that suction fan 16 at the end of thefirst system may withdraw a stated amount of air throu h duct 13. Theinterposed co1 lecting cham ers 14 serve the purpose merely of savingany material that may be carried over past collecting chamber 10. Bycompletely closing valve 32, only fresh air drawn into duct 18 throughopening 30 will be passed through heater 20 and thence through the firstrotary drum and connected apparatus,

such air thereupon passing into the first circutinued in circulation,will depend upon the setting of valve 33. Ordinarily the best resultswill be secured by introducing fresh air through opening 30 at a ratejust sufficient to prevent the air from becoming over saturated as it iscirculated through the successive systems and the rate of transfer ofair from the second to the firstsystem can be nicely regulated bymeansof valves 32 and 33. The suction fan 16 of course can withdraw airfrom such first system no faster than it is admitted through opening 30to the second. 7

It will be apparent that where in handling any particular material thelatter can be reduced to a sufiiciently dry state by one opertwo stages,it will be evident that a third cir- .culatory system may be coupledonto the second system, as shown, in the same manner as the latter iscoupled onto the first in the illustrated form of our apparatus.

Other modes of applying the principle of our invention may be employedinstead of the one explained,'change being made as regards the means andthe steps herein disclosed, provided those stated by any one of thefollowing claims or their equivalents be employed.

We therefore partlcularly point out and distinctly claim as ourinvention 1. In a rocess for drying-materials, the

steps'whic consist in pulverizing and agltating the material to bedried, at the same time passing through such material a gaseous currentcapable of absorbing mosture there-- from, such current beinghifsuflicient force to separating such particles from such current,returning the latter for use over again, further pulverizing andagitating the-material separated as aforesaid, passing therethroughanother gaseous current capable of absorbing moisture therefrom, suchcurrent/being of sufiicient force to carry alon the dried particles ofthe material as be ore, separating such particles from such current,returning the latter for usevover again in the lastmentioned moistureabsorbing step, gradually replacing a portion of such last-mentionedcurrent with fresh gas, and similarly replacing a portion of suchfirst-mentioned current With gas fromsuch last-mentioned current.

2. In mechanism of the character described, the combination of amaterial pulverizing and agitating device, a duct adapted to form aclosed circuit with such device included therein, means adapted tocirculate a gaseous moisture-absorbent medium through said duct, meansinterposed in the latter adapted to separate out particles of thematerial carried along by such medium, a second pulverizing andagitating device connected to receive the material from said separatormeans, a duct adapted to form a closed circuit with such second deviceincluded therein, means adapted to circulate a gaseousmoisture-absorbent medium through said secondduct, means interposed inthe latter adapted to separate out particles of the material carriedalong by such medium as before, means adapted gradually to Withdrawqaportion of'such medium from said first duct, and a connection from saidsecond duct to said first duct, said second duct being provided with anopeningat one point for the supply of fresh medium thereto and throughsaid connection to said first duct.

Signed by us, this 6th day of February,

WILLIAM J. HARSHAW. CHARLES S. PARKE.

